1. Field
Devices consistent with the exemplary embodiments relate to an image display device, and more specifically, to a glass-free image display device having an improved structure for implementing a two-dimensional (2D) and three-dimensional (3D) image.
2. Description of the Related Art
Stereoscopic image display devices implement a 3D image using a stereoscopic technique or an auto-stereoscopic technique. The stereoscopic technique uses a parallax image between a user's left and right eye which has a great stereoscopic effect. The stereoscopic technique may be classified as a glass type or a glass-free type technique.
In the glass type technique, an image is displayed on a direct-view display device or a projector by changing a polarization direction of the parallax image between the left and right eye or by using a time division method. A stereoscopic image is implemented using polarized eyeglasses or liquid crystal shutter eyeglasses. In the glass-free method, a stereoscopic image is implemented by installing optical components, such as a lenticular lens, and a parallax barrier in front of and behind a display screen in order to separate an optical axis of the parallax image between the left and right eye.
As an example of the glass-free methods, in a method of using the lenticular lens, a 3D stereoscopic image is implemented by separating a right-eye image and a left-eye image using the lenticular lens. In the method using the lenticular lens, since it is impossible to turn optical separation of the lenticular lens on and off, only the 3D stereoscopic image is implemented and conversion between the 3D stereoscopic image and a 2D plane image is not possible.
In order to address problems related to the use of the lenticular lens, a crystal lenticular lens capable of converting a 2D and 3D image, in which a lenticular lens is implemented by electrically controlling a refractive index of a liquid crystal, has been proposed. However, such a liquid crystal lenticular lens has a problem in that an arrangement direction of liquid crystal molecules needs to be adjusted in accordance with a 2D image and a 3D image, the lens is expensive, and a large scale lens is difficult to manufacture.
As another example of the glass-free methods, a parallax barrier method is more advantageous than the lenticular lens method in terms of a cross-talk and a view angle, but luminance may decrease, and two sheets of cells need to be used since an image cell and a barrier cell are composed of a double structure.